Mining techniques can be divided into two common excavation types: surface mining and sub-surface (underground) mining. Today, surface mining is much more common, and produces, for example, 85% of minerals (excluding petroleum and natural gas) in the United States, including 98% of metallic ores.
Mining of Iron Ores. Iron ore is a type of mineral and rock from which metallic iron is extracted economically. This ore is normally rich in iron oxides and vary in color from dark grey, bright yellow and deep purple to rusty red.